This invention relates to the field of frequency synthesizers and more particularly to synthesizers which can sample and hold a received frequency.
Synthesizers which can provide an output signal of a desired frequency and harmonic content are well known in the art. It may, however, be desirable to let a brief input signal determine the frequency of a sustained synthesizer output signal. The input signal might be an audio frequency signal as from a microphone. In the field of musical instruments it may also be necessary to measure very accurately an audio signal, such as from one of the percussion instruments, which is produced for only a brief period and which, during that period, may change rapidly in amplitude and/or frequency. If such a signal could be sustained for a substantial period, accurate measurement of the frequency becomes possible. In RF circuitry, it may also be desirable to sample a brief RF signal and lock an oscillator onto that frequency for a substantial period of time.